Some relays can literally sell information like when you are connected, from which IPs and thus locations, what searches do you make and which posts are you looking at in real time. Lots of companies buy that information.
Discussion
What I wrote didn’t make sense but it seems like you got what I was trying to say.
Fair point regarding the scope of information they have, and yeah, I can see some concern down the line.
I have to think through it some more and keeping an open mind, but the way I’m seeing it right now is if you’re using a public relay that you aren’t paying for then yeah, you’d run that risk. If it’s a paid relay and part of their ToS is not selling your information, then that’s the safer route for the end user.
Though I think for notes to proliferate you’d inevitably have to connect to at least 1 or more public relays that public goods.